1. Field of the Invention
The present invention relates to a light source device that enables special light observation using many kinds of special light such as narrow-band light, fluorescence, and infrared light, in addition to normal light observation by white light.
2. Description of the Related Art
Conventionally, an endoscope is used for observing an alimentary tract such as the esophagus, the stomach, the small intestine or the large intestine, or for observing tracheae such as the lungs by inserting an elongated insertion portion into the body. An endoscope also makes it possible to perform various kinds of examinations or curative treatments by passing a treatment instrument through a treatment instrument channel provided in the insertion portion of the endoscope.
When performing an examination, tissue extraction, treatment or the like using an endoscope, a light source device that supplies an illumination light, a control device such as a video processor that generates video signals from optical images of an examination site that are picked up by the endoscope, and a display device that displays endoscopic images of the examination site and the like are used as peripheral endoscopic devices.
In recent years, when performing diagnosis using an endoscope, in addition to normal light observation by white light in which color images of an observation site are displayed on a display device and observed, special light observation is performed that employs fluorescence, infrared light, narrow-band light (also described as “NBI”), and the like as illumination light.
Special light observation makes it possible to, for example, bring blood vessels on the surface of an alimentary tract into clear view for displaying on a display screen. It is therefore possible to distinguish cancer locations that are difficult to find with normal light observation, or to distinguish the size of a cancer or whether a tumor is cancerous or is in a precancerous state or the like.
There is thus a demand for light source devices that, in addition to white light for performing normal light observation as an illumination light, also provide a plurality of kinds of special observation lights as illumination lights. Examples of special observation lights include fluorescence for performing fluorescence observation, infrared light for performing infrared light observation, and NBI for performing NBI observation.
For example, Japanese Patent Application Laid-Open Publication No. 2005-006974 discloses an endoscope apparatus in which, by means of an operation to switch an observation mode, it is possible to only select an observation mode that is compatible with a connected endoscope, and perform observation in that mode. In this endoscope apparatus, as illustrated in FIG. 1, a lamp 101, a filter turret 103, an illumination light aperture (not shown), a rotary filter 104, a rotary motor 105, and a light-condensing device 106 are provided inside a light source device 100. The filter turret 103 is configured to be capable of switching a plurality of optical filters (not shown) by driving of a motor 102. The transmission wavelength bands of the plurality of optical filters differ for each observation mode. The illumination light aperture limits the irradiation light amount. The rotary filter 104 changes the illumination light into, for example, frame sequential light of red (R), green (G), and blue (B). The rotary motor 105 rotatingly drives the rotary filter 104. The light-condensing device 106 includes a lens 106a. The lens 106a of the light-condensing device 106 condenses the frame sequential light onto an incidence plane 112 of a light guide 111 of an unshown endoscope.
The rotary filter 104 includes filters 107 and 108 on the outer circumference side and inner circumference side, respectively. A forward/rearward movement motor 109 that moves the rotary filter 104 forward/rearward in a perpendicular direction to the illumination light path (hereafter, referred to as “optical path”) is provided inside the light source device 100. The rotary filter 104 is thus moved forward/rearward by driving of the motor 109. More specifically, the rotary filter 104 is configured to change between a state in which the rotary filter 104 is moved to a position indicated by the solid line so that the outer circumference side filter 107 is disposed in the optical path and a state in which the rotary filter 104 is moved to a position indicated by the dashed line so that the inner circumference side filter 108 is disposed in the optical path.
According to the light source device 100, by switching the optical filters of the filter turret 103, suitably combining rotary operation of the rotary motor 105 with forward/rearward operation of the forward/rearward movement motor 109, and selectively controlling switching of the filters 107 and 108 provided in the rotary filter 104, it is possible to carry out endoscopic observation which switches among a plurality of observation modes.
However, recently various kinds of special lights that are useful for observation have been developed. There is thus a demand from users for a light source device that enables observation using even more kinds of special light. In a light source device, it is possible to perform observation by various kinds of special light by increasing the number of optical filters. For example, in a light source device 100A shown in FIG. 2, a rotary filter 104A is additionally provided to increase the number of filters. However, by additionally providing the rotary filter 104A in the optical path, the position of the lamp 101 of the light source device 100A is displaced by an amount L1 in comparison to the position of the lamp 101 of the light source device 100 shown in the aforementioned FIG. 1. As a result, a disadvantage arises that the size of the light source device increases.
In a light source device 100B shown in FIG. 3, a rotary filter 104A that is additionally added is disposed facing the rotary filter 104, and the rotary motor 105 is provided on the light-condensing device 106 side. According to this configuration, when the rotary motor 105 is moved to the optical path as indicated by the dashed line, interference occurs between the rotary motor 105 and the light-condensing device 106. Accordingly, a motor relief part 114 as illustrated by a chain double-dashed line is provided in a lens base 113 comprising the light-condensing device 106 as shown in FIG. 4.
In this connection, the dashed line position is a position at which the rotary filter 104A and the rotary motor 105 are separated the most from the optical path. In other words, the rotary filter 104A and the rotary motor 105 advance and retreat to disposition positions indicated by the dashed line and the solid line. According to this configuration, interference between the rotary motor 105 and the light-condensing device 106 is prevented, and the position of the lamp 101 of the light source device 100B and the position of the lamp 101 of the light source device shown in the aforementioned FIG. 3 are substantially the same position. Thus, it is possible to perform observation using many kinds of special lights without making the light source device 100B larger than the light source device 100.